<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    div {
        width: 200px;
        height: 200px;
        background-color: pink;
    }
</style>
<body>
    <div></div>
    <script>
        var div = document.querySelector('div');
        // js 修改行内样式
        div.onclick = function() {
            this.style.backgroundColor = 'red';
            this.style.width = '300px';
        }
    </script>
</body>
</html>